Home' Grower : May 2010 Contents The South Australian Grower -- May 2010
Correct food paths lift
strength of SA crops
By RICHARD EMERY
EACH season trees work hard to convert
sunlight into carbohydrates in the leaves,
before sending this 'food' into the
developing fr uit to deliver a crop.
Food movement is all about the points of
demand and the signals that determine food
movement are determined by hormones.
Hormones determine the greatest sink for
food at different growth stages and these
sinks will change in strength. At times, most
of the food is directed to the vegetation,
while at other times most of the food is deliv-
ered to the fr uit or a stronger sink from the
roots and storage tissue is obser ved.
The main hormone that directs food is
indoleacetic acid. When IAA moves down
from the vegetation, sugar and carbohydrates
move in the opposite direction -- up to the
shoots. When IAA moves from the fruit,
food -- sugar and carbohydrates -- move in the
opposite direction, or into the fruit.
Leading up to har vest, if the crop is managed
properly, most of the food should have been
moving to the fruit. This is where the produc-
tion comes from. If there is a big fr uit load,
the fruit should be sending IAA out and
receiving food from the leaves in return. Too
much late vegetative growth can lessen the
tree's ability to size its fruit, because the vege-
tative growth competes with the fruit for food.
When the fruit is har vested, the largest sink is
suddenly lost. The trees are still producing
food and the food has to go somewhere.
Where will the food go now? It will go to the
point that is presenting the next biggest sink. It
will be most likely shared amongst the vegeta-
tion, the roots and the storage tissue in the tree.
Growers do not want the food to move to
the vegetative growth because that will be
falling on the ground soon. Instead, a move
to the roots and storage tissue is desired. The
storage tissue includes the buds that will be
important next season so it helps if they are
furnished with food. Movement to the roots
keeps the roots alive for longer and keeps
their ability to supply water and nutrients to
the trees as they approach dormancy.
There is valuable food stored in the leaves.
After har vest it is best if this food moves back
into the tree and not into new vegetation. If
possible, the vegetative growth should slow
down leading up to har vest so that all the ener-
gy is not put into feeding the new vegetation.
Once the tree has settled after har vest, there is
a good opportunity to provide food, especially
if the tree is in storage mode. The tree stores
reser ves in the roots and woody tissue and
these reser ves are critical to healthy growth in
the spring. Many species of tree rely on
stored arginine nitrogen for a large part of
their spring growth. This can be applied to
the tree in post har vest treatments. Many
secondary and micronutrients can also be
applied at this time. Most trees experience a
root growth flush after har vest so this is a
good time for soil applied fertiliser.
Suggestions for post har vest practices
• Avoid practices that will promote vegetative
growth close to har vest time such as heavy
irrigations or high nitrogen applications.
• Make sure nutrient elements are at opti-
mum levels especially potassium, magne-
sium and boron.
• Immediately after har vest, irrigate wit
out fertiliser to reduce stress
• Follow up with a post har vest nutrient
treatment for the tree -- this provides the
reser ves that are needed for the next
Stoller Australia has a range of options for
hibernation. Where a crop is growing vigor-
ously, a foliar treatment of Sugar Mover can
help direct food back to the storage tissue and
roots. This often applied with Stoller's ZM2
and Foli-Zyme. In cases where the tree is not
adequately returning carbohydrates to the
storage tissue after har vest, Sugar Mover has
been shown to enhance budburst when used
as a post har vest foliar spray.
Through the irrigation, Post Har vest 23
will provide amine nitrogen, calcium and
magnesium and if root health is an issue
RootFeed (containing root stimulants) can
be used instead.
Details: Stoller Australia 1800 337 845,
email@example.com or stoller.com.au
Post harvest leaf growth a waste
Push food into buds and roots
Management improves next crop
AT A GLANCE
When a tree is in a vegetative mode, it
directs food and energy from the roots and
storage tissue to the leaves.
Once in storage mode, the tree directs all of
its food and energy into the storage tissue
and root system.
Registered trademark of a Syngenta Group Company ABN 33 002 933 717. All products written in upper case are registered trademarks of a Syngenta Group Company.
For further information on products please contact the Syngenta Technical Advice Line: Freecall 1800 067 108 or visit our web site at www.syngenta.com.au
Syngenta Crop Protection Pty Limited, Level 1, 2-4 Lyonpark Road Macquarie Park NSW 2113.
Single feed results,
no resistance worldwide
and available at rural
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